1. Field of the Invention
The present invention relates to a swing analyzing device comprising a swing practice equipment such as a golf club or the like.
2. Description of the Related Art
Typically, a video camera is used when practicing to improve a golf swing, since a locus of a swing can be visually reproduced by a continuous or still photographic playback of pictures taken by the video camera.
Nevertheless, problems arise in the visual reproduction of a locus of a swing as a continuous photographic playback, in that it is difficult to accurately reproduce a component of a movement that is perpendicular the point from which a picture is taken, because a three-dimensional movement cannot be actually depicted, i.e., only a planar picture can be obtained, and if the body of the player is twisted, and thus a desired target portion of the body is hidden by the twisted body, it becomes impossible to show such a target portion in the picture. Also, when using a standard camera, it is difficult to take an instantaneous shot of the impact of the golf club with the golf ball, and expensive high speed cameras must be used for this purpose. Further, video cameras are not able to carry out a numerical analysis, or an analysis similar to a numerical analysis. For example, a difficulty arises when it is desired to continuously output outlines of only a locus of a golf club swing, as a picture or display wherein the background is removed (hereinafter referred to as a stick picture). In an analysis using a video camera, it is necessary to digitize a coordinate of a target portion of a moving body from the picture of the swing, and this must be repeatedly carried out at very small intervals, and such work is laborious and time consuming. Accordingly, it is impossible to display a stick picture just after a swing has been made.
Therefore, when practicing a swing, such as a golf swing, a problem arises in that analysis data cannot be obtained just after the swing has been made, and therefore, a desired improvement of a swing by practice or training of a swing is not easily obtained. Further, such a practice motion must be repeated many times, and therefore the analysis of a practice swing must be able to be made at a low cost. With the conventional methods, however, it is impossible to carry out a swing analysis at a low cost and with a real time processing.
Japanese Examined Patent Publication No. 61-15713 discloses a method of obtaining a locus of a swing of a golf club on a display, by attaching a three-axes acceleration sensor (an acceleration sensor capable of detecting accelerations in three directions X, Y, and Z) to the golf club, and calculating a displacement of coordinates at particular points during the swing, to thereby obtain a locus of a swing of a golf club.
In this swing analyzing device, a signal from the acceleration sensor denotes an acceleration on an inertia coordinate, i.e., a coordinate on a moving body, but a swing is not a linear movement, and therefore, it is impossible to obtain a locus of a swing on an absolute coordinate merely by attaching an acceleration sensor to a golf club. Also, the three-axes acceleration sensor is large and heavy, and thus the characteristics of the golf club, such as the weight and balance of the golf club, and the flexure of the shaft, are changed, and thus the swing is affected and it becomes impossible to analyze an actual swing of a standard golf club.